>In The Dawn of the Third Age peter.unmack at ASU.Edu woke me from my
>contemplation by writing:
>
>>On Thu, 6 Feb 1997, Bruce Hansen wrote:
>>> I am just thinking of the RF Blue-eyes and the rather low success rate that
>>> seems to be evident in maintaining high fertility on-going vigorous strains
>>> in captivity.
>>
>>Is it genetic or environmental? :-) It's a hard question to answer
>>seeing we have no genetic information at all.
>
We should have some DNA analysis very soon. I have a lab analysing specimens
form all known populations. Perhaps not enough to be significant, but we may
get some idea. Don't write me Peter re this; results are due by March and I
will publish as soon as I can.
>I wonder if any one has tried to simulate the daily temperature change
>with this species? Say possibly putting the tank in a cold location
>and having the heater on a timer to kick the water temperature to a
>high level for a few hours each day.
I think temperatures for spawning should be in the high end of the range ie
25 to 35 degrees celcius, and never below about 18 degrees. Spawning
displays are less frequent in the wild during the cooler months. In summer
the variation in water temp is not great. In winter, water temperature
variation in preferred habitat is perhaps 5 to 15 degrees.
Does it appear there is a lack of
>spawning activity and eggs, or a lack of fertile eggs? If its a lack
>of spawning activity then folks need to search for a trigger.
I think the problem with the captive populations is that the males spend too
much time displaying to each other, and not enough time with the females.
Hence low egg production and/or fertility. In the wild each male defends a
transient territory which is usually not in direct view of to many other
males. The territories are visually separated by emergent vegetation. Males
spend most of their time displaying to females. Large shools of females and
immature males (10 to 100) travel between males territories, feeding and
spawning. In captivity males spend a great deal of their time displaying to
other males, because they are all invariably in direct view of each other.
>Or maybe they just need a few dambusia to beat up to get them in the
>mood:~)
The males get side tracked displaying at Gambusia; they have no idea!
A bit later on Cary wrote also:
> Unfortunately I don't think enough is know about
>how they reproduce in the wild to extrapolate on. Maybe they even need
>poorer water conditions to trigger proper maturation of sperm and
>eggs. If anybody should have an idea of the annual water conditions
>cycle you should, or at least know who to talk to Peter.
The water quality parameters in springs with rfbe do not appear to vary
significantly over a year, except for temperature (of course). Irregular
increases in ammonia do occur in some springs. This is caused by wastes from
livestock. When this happens the fish move away from the polluted areas.
Its hard to
>believe that alleles could have degenerated in so few generations, as
>to make the species nonviable. Particularly a species living in such
>limited numbers in such small water holes.
I agree. I think the answer to increasing spawning and recruitment in
captivity is still in provision of suitable environmental conditions in tune
with their natural behaviour. Consider large shallow tanks (4 to 6 feet
long, 6 inches high) with opaque baffles to provide a basis for easily
defenable territories. Retain offspring (especially females) to allow
individual captive populations to reach a large size. Maybe pick of the
large males that have held a terrritory for some time and swap these or put
them in a display tank.
Cheers
Rob Wager
Freshwater Fish Biologist
Raintree Aquatics Pty Ltd
Aquatic Environment, Fish and Aquaculture Specialists
1002 Caboolture River Road, Rocksberg, Queensland, Australia, 4510
Phone 07 5496 7939, Facsimile 07 5497 0022, International +61 7 5496 7939
Email raintree at closer.brisnet.org.au